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<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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    <script>
        /* 正则
        我们写的正则表达式，只要符合字符串的某一段就可以了
         */
        var str = "abc3824793847"
        var reg = /\d{3,5}/
        console.log(reg.test(str));
    </script>
</body>
</html>